The present invention is generally directed to adjustable clamps and methods for controlling the rate of fluid flow through flexible plastic tubing and more particularly to an adjustable clamp and method for controlling the rate of fluid flow through flexible tubing such as used for intravenous infusion of liquid nourishment and/or medication.
The intravenous infusion of medicinal fluids is quite common in current medical practice. For example, anesthetics are infused intravenously during operations, and intravenous feeding is commonly employed in the post operative period. In addition, there are many patients whose illness either restricts their ability to take food orally or to digest food properly so taken, and then such patients must be fed intravenously for the duration of their illness.
The apparatus commonly employed for intravenous infusions includes a stand for supporting a bottle of the appropriate fluid in an elevated position above the patient. The bottle of fluid is supported in an inverted position to induce gravity flow of the fluid. A sterile intravenous set comprising a flexible plastic tubing and a plastic spike at one end of the tubing conducts the fluid from the bottle to the patient by gravity feed. The spike end of the flexible tubing is inserted into the bottle stopper and the needle is inserted into the patient's vein using approved sterile techniques. All air is eliminated within the tubing before the patient is infused by allowing the fluid to completely fill the tubing. The flow rate of the fluid through the tubing is controlled by an adjustable clamp on the tubing. The clamp controls the fluid flow rate by controlling the cross-sectional area of the tubing. In order to measure the flow rate with these devices it is necessary to count visually the number of drops of fluid per minute by watching the drops in the drop chamber located below the spike.
In the past, a problem has been encountered in maintaining a constant fluid flow rate through the flexible plastic tubing (usually polyvinyl) because of its physical characteristics. After the desired fluid flow rate has been set with the adjustable clamp, as by restricting a portion of the cross-section of the tubing, the plastic wall of the tubing tends to cold flow or deform slowly resulting in a progressive change in the cross-sectional area through which the fluid is flowing thereby progressively changing the fluid flow rate through the tubing. This requires frequent adjustment of the clamp in order to make sure that the correct fluid flow rate is maintained. Tests have shown that the standard intravenous set loses an average of 45% of its initial flow rate in ten minutes if not readjusted.
The adjustable clamps and methods fully disclosed and claimed in U.S. Pat. No. 4,034,773 which issued on July 12, 1977 in the name of the inventor of the present invention has significantly reduced the flexible tubing cold flow problem referred to above. The present invention provides a still further improvement on the invention in the aforesaid patent.
Another problem with prior art adjustable clamps for use in intravenous feeding is that they cannot be applied to the flexible tubing without disturbing the sterility of the intravenous sets. Intravenous sets are commonly supplied to medical facilities by suppliers who provide their own control clamps as a part of the sets. Unfortunately, these clamps cold flow and prior art clamps which control cold flow cannot be attached to the tubing of the finished set. The reason for this is that the prior art clamps are not adapted to be applied directly to the flexible tubing without disturbing the set sterility. Hence, there is a need in the art for a clamp which may be applied to the flexible tubing of an intravenous set for controlling cold flow without disturbing the sterile condition of the intravenous set.